Targeting device for guiding a drill arrangement

ABSTRACT

A targeting device ( 1 ) for guiding a drill arrangement ( 11, 12 ) for forming an arc-shaped bore in an assembly of adjacent bones or bone fragments, comprises a support frame ( 2; 5; 7 ), a pivoting device ( 8 ) mounted to the support frame ( 2; 5; 7 ) and arranged to receive the drill arrangement ( 11; 12 ) and to allow a pivoting movement of the drill arrangement ( 11; 12 ) along an arc-shaped path having a predetermined radius of curvature r c  around a pivot axis ( 9 ). The support frame ( 2; 5; 7 ) is provided with at least three fixation devices ( 3; 4; 6 ) each configured to fix one of the bones ( 14; 15; 16 ) or fragments of the bone assembly to define a fixed position in space of the bone assembly ( 14; 15; 16 ) with respect to the pivoting device ( 8 ) when the bone assembly is installed to the support frame ( 2; 5; 7 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

The present disclosure claims the benefit of U.S. Provisional Patent Application Ser. No. 61/726,358, filed Nov. 14, 2012, the contents of which are hereby incorporated by reference in their entirety, and claims priority from European Patent Application EP 12192679.4, filed Nov. 14, 2012, the contents of which are hereby incorporated by reference in their entirety.

BACKGROUND

The invention relates to a targeting device for guiding a drill arrangement for forming an arc-shaped bore in an assembly of adjacent bones or bone fragments, respectively.

From document WO 2011/072249 A1, a guidewire targeting device for assisting in the arthrodesis of the heel is known that allows to form two straight cutting paths starting from a bottom section of the calcaneus and extending through the talus towards the tibia canal using guide wires, which are angled relative to each other. Using a drill and a reamer after removing the targeting device, a bent bore or canal may be established from a combination of paths that may receive an immobilizing nail. Tubular sleeves are used in the targeting device to guide the wires straight through the bone material.

This approach, however, suffers from an increased damage of bone material as two cutting paths are applied. Further, the patient may suffer from pain, when the bottom portion of the calcaneus is involved in the surgical process. Moreover, duration and stability of the overall configuration may not be satisfactory. Therefore, in some surgical applications, a further need for forming bores in bone material departing from the commonly applied straight shape has arisen in the recent past.

Some of those applications relate to drilling arc-shaped bores into one bone or in an assembly of multiple adjacent bones.

A device for forming an arcuate channel in vertebrae has, for example, been proposed in US 2005/0267481 A1, wherein two path-guard members connected with each other via a platform assembly are attached to each one vertebra by multiple nails, respectively. A pivot arm mounted at the platform holds an arc-shaped tube member through which a drive cable extends that is driven by a motor such as to rotate a drill bit arranged at a front end of the tube member. Due to the arcuate shape of the tube an arc-shaped bore hole can be drilled when the pivot arm is advanced towards the bone. In this manner, an intervertebral disk directly accessed through the arc-shaped bore that is cut into adjacent vertebral bodies and through respective end faces thereof.

Another device for forming a bore in an arcuate shape is described in US 2010/0292722 A1. The device comprises a main body attached to the heel of the human body by means of Kirschner-wires, and an arc-shaped guide enables guiding a tube having a corresponding radius of curvature r_(c) to perform a pivoting movement. The device is attached to the heel at two locations. A drill bit driven by a motor via a drive cable extending through the tube enters into the calcaneus first, and then advances the arcuate-shaped bore through the talus into the marrow space of the tibia. The circular arc-shaped bore thus formed allows inserting a corresponding nail which immobilizes the bones involved.

SUMMARY

It is an object to provide a targeting device, which improves the accurateness of a drilling process, or which allows a more accurate control of the same.

The object is solved by a targeting device according to claim 1.

The targeting device provides for at least three different fixation devices, which allow fixation of each a single bone or bone fragment of a bone assembly. The fixation devices are provided being mounted at a common frame. A pivoting device is also provided and is configured to be mountable to the frame. The pivoting device holds the drill arrangement and allows to advance the drill arrangement by a pivoting movement that is performed along an arc-shaped path within the plane.

The position of the bone assembly is completely defined by fixation at three points in space due to the three fixation devices. As a consequence, an arc-shaped path along which drilling takes place by virtue of the pivoting movement of the drill arrangement is fixed relative to the bone assembly. Hence, no deviations such as drifts or the like may occur and the accurateness of the arc- shaped bore is improved. This may be important when an arc-shaped nail may be inserted afterwards, which is designed to immobilize the bone assembly, and whose shape has to correspond to the arc-shape of the bore.

In one specific embodiment, the targeting device comprises a drill jig. The drill jig has a jig portion which allows to indicate a position of the arc-shaped bore before, during or after drilling. The drill jig may be provided as a separate part from the privoting device, or may also be formed connected with the pivoting device. The drill jig may pivot around a same pivot axis as the pivoting device. In one specific embodiment, the drill jig and the pivoting device may be provided as separate parts removable from the frame, wherein one part is replaced by the other during use of the targeting device.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the invention will become apparent from the description of an embodiment by means of the accompanying drawings. In the drawings:

FIG. 1: shows an overview of a targeting device according to a specific embodiment and with a drill arrangement in a perspective view;

FIG. 2: shows in a perspective view details of the main support as shown in FIG. 1 with first and second fixation devices;

FIG. 3: shows in a perspective view details of the first pivotable support portion as shown in FIG. 1 attached with a third fixation device;

FIG. 4A: shows in a perspective view details of the second pivotable support portion as shown in FIG. 1 attached with a third fixation device;

FIG. 4B: shows an enlarged view of the C-shaped receiving portion of FIG. 4A with a pattern of ribs;

FIG. 5: shows in a perspective view details of the pivoting device and the drill arrangement as shown in FIG. 1;

FIG. 6: shows in a perspective view details of the drill jig as shown in FIG. 1;

FIG. 7: shows details of a bone anchor having a tulip head as used in connection with the targeting device of FIG. 1;

FIG. 8: shows a step of using the targeting device of FIG. 1 in a perspective view of the heel with two bone anchors having a tulip head being inserted into the calcaneus and talus, respectively, in a side view;

FIG. 9: shows the same as in FIG. 8, but in a front view;

FIG. 10: shows the same as in FIG. 8, but in a back view;

FIG. 11: shows a further step of using the targeting device in a perspective view of the human foot wherein in a schematic representation (dashed lines) Kirschner-wires are inserted to reposition bones of the heel;

FIG. 12A: shows a further step of using the targeting device wherein the human foot is installed to the main support with the first and second fixation (soft tissue parts not shown);

FIG. 12B: shows an enlarged view of a connection established between a tulip head of the bone anchor and a ball head protruding from a tip of a pin provided at the first fixation device;

FIG. 13: shows a further step of using the targeting device wherein the first pivotable support portion with the third fixation device is mounted to the main support, and the fixation device is fixed at the tibia;

FIG. 14: shows a further step of using the targeting device wherein the drill jig and the second pivoting portion is swivelled to find an appropriate rotational position of the pivot axis defined at the second pivoting portion to drill the bore;

FIG. 15: shows a further step of replacing the drill jig and attaching the pivoting arm and the drill arrangement to the pivot axis of the targeting device;

FIG. 16: shows a further step of advancing a drill bit and circular arc-shaped tube of the drill arrangement into the bore by pivoting the pivoting device;

FIG. 17: shows an example of a circular arc-shaped bone nail inserted into the bore formed according to the method of using the targeting device.

DETAILED DESCRIPTION

An embodiment of a targeting device 1 that holds and guide a drill arrangement 11, 12 is shown in FIG. 1. The assembly shown in FIG. 1 is specifically designed for drilling circular arc-shaped bores through bones of the heel of the human body. The application is designed particularly to perform arthrodesis of the hindfoot. Similar arrangements may be configured for application to other parts of the human body without departing from the scope of the appended claims.

FIG. 1 provides for an overview, while details of its components are shown in FIGS. 2 through 7, and wherein steps of preparing the human foot and heel, of using the targeting device and of operating the drill assembly are shown in FIGS. 8 through 16, respectively. A bone nail compatible and insertable into the bore drilled by using the drill arrangement according to FIGS. 1-7 and to the method according to FIGS. 8-16 is shown in FIG. 17.

In FIG. 1, the targeting device 1 includes a frame or framework which basically comprises a main support 2 with a first pivotable support portion 5 and a second pivotable support portion 7. The main support 2 is further configured to receive first and second fixation devices 3, 4, and the first pivotable support portion 5 is configured to receive a third fixation device 6.

The targeting device of this embodiment further includes a pivoting device 8 that is adapted to hold a drill tool 11 and a circular arc-shaped tube portion 12 with drill bit. The pivoting device 8 can be attached to a rotational support 72 at the second pivotable support portion 7. The rotational support 72 defines a pivot axis 9 that is—in this specific embodiment—substantially perpendicular to a plane spanned by parts 2, 5 and 7. A rotatable drill jig 10 may also be attached to the rotatable support of the second pivotable support portion 7. In FIG. 1, pivoting device 8 and drill jig 10 are indicated as an integral part. Due to the above construction, the planes in which the pivoting device 8 and the drill arrangement as well as the drill jig rotate, is substantially parallel to the plane spanned by the frame parts 2, 5 and 7.

As shown in FIG. 13 described in more detail below, the fixation devices 3, 4 and 6 are designed to be fixed at bones or bone fragments of the bone assembly of the heel, in this specific embodiment calcaneus 14 (fixation device 4), talus 15 (fixation device 3) and tibia 16 (fixation device 6). In order to meet the specific anatomy of the respective heel, the fixation devices 3 and 4 can be slidably adjusted in linear fashion with respect to each other, and the third fixation device 6 may also be slidably adjusted on the first pivotable support portion 5. Further, the third fixation device 6 can be rotated with respect to the position of the other two fixation devices 3, 4 by rotating the first pivotable support portion 5.

On the right side of the arrangement, the second pivotable support portion 7 can also be rotated with respect to the main support 2, wherein the second pivotable support portion 7 provides at an end section 7 a opposite to an end section 7 b connected to the main support 2 for the rotational support 72 which defines the pivot axis for the pivoting device 8 with the drill arrangement 11, 12 or the drill jig 10.

The drill arrangement comprises the drill tool 11 and the tube portion 12 with drill bit 126 that is received and held by the pivoting device 8. The tube portion 12 is circular arc-shaped as shown in FIG. 1. The tube portion 12 has a radius of curvature r_(c), which corresponds to its distance from the pivot axis 9 such that when the pivoting device 8 is rotated about pivot axis 9, the tube portion 12 moves along its own curved central axis. As a consequence, when a user adjusts the rotation angle of the second pivotable support portion 7 with respect to the main support 2, a circular or circular segment path described by the movement of the tube portion 12 and the drill bit 126 can be positioned relative to the bone assembly of the heel of the patient, as will be described in more detail with reference to FIG. 14 below.

The individual components of the targeting device 1 and the drill arrangement 11, 12 are shown in more detail in FIGS. 2 through 6. FIG. 2 shows details of the main support 2. The main support 2 of this specific embodiment comprises guide rails 20, 21 which are arranged in parallel. At one end of the guide rails, the first fixation device 3 is arranged and at the other end the second fixation device 4 is arranged. The first fixation device 3 is slidable while the second fixation device 4 is fixed on the guide rails 20, 21. Nevertheless, other embodiments may also allow for both fixation devices 3, 4 being slidable.

The second fixation device comprises a (fixed) carriage 42, which has a pinch wheel 41, a base part 42, a vertical part 45 extending vertically from the base part 42, a pin 46 which protrudes horizontally from the vertical part 45 and a ball head 47 arranged at the tip of the pin 46. The pinch wheel 41 is arranged at the bottom of the carriage 42 and is configured to clamp or pinch the end section 7 b with a C-shaped receiving portion 71 and a pattern of miniature ribs 73, described below with reference to FIGS. 4A and 4B.

The pinch wheel 41 may be rotated with respect to a cylindrical portion (not shown) having a thread cooperating with an inner thread provided at the pinch wheel 41 and defining a vertically extending axis 92 such as to increase or decrease its distance towards a bottom face of the carriage 42. Manual fine adjustment of the pinch wheel allows to determine a desired tactile response due to the pattern of miniature ribs 73 provided at the side of the second pivotable support portion 7, when the latter is rotated around above axis. A pattern of miniature ribs 73 (not shown) arranged to cooperate with ribs 73 at the second pivotable support portion 7 may therefore also be provided at the bottom face of the carriage 42. Further tightening of the pinch wheel 41 then allows a final locking of the orientation of the second pivotable support portion 7, when the ribs 73 on both sides securely engage into corresponding grooves between ribs 73 on the other side.

The carriage 42 includes holes 43, 44 for receiving the guide rails 20, 21, respectively, and also has the vertical part 45, the horizontal pin 46 and the ball head 47 at its tip to facilitate fixing of a part of a bone, more specifically the calcaneus. The pin 46 and ball head 47 form a receiving portion of the second fixation device 4. Thereby, the ball head 47 is configured to interact with a tulip head 130 of a bone anchor 13 that is shown in FIG. 7. Such bone anchor 13 for this purpose is anchored in the calcaneus by virtue of its threaded shaft 131. The ball head 47 may snap into the tulip head 130 which has a resilient upper edge portion due to notches 132.

The connection between the ball head 47 and the tulip head 130 provides for one of the fixation points (out of at least three) between the targeting device 1 and the bone assembly. In this specific embodiment, the ball-joint-like connection established by the second fixation device as described above provides for some small degree of freedom for polyaxial orientation of the components with respect to each other—as long as less than three fixation points have yet been established, eventually leading to the fixation of the bone assembly in three dimensional space.

As shown in FIG. 2 the first fixation device 3 is slidably arranged on guide rails 20, 21. Sliding adjustment and fixation of a position is accomplished by screw 35. Similar to the second fixation device 4, the first fixation device 3 has a carriage 42 with a pinch wheel 31, a vertically extending part 39, a horizontally protruding pin 37 and a ball head 38 at its tip. The function of ball head 38 is the same as in case of ball head 47 of the second fixation device. The pin 37 and bal head 38 form a receiving portion of the first fixation device 3. As shown in FIG. 12A, the pins 37, 46 protrude horizontally towards end faces of the talus and calcaneus, respectively, when the human foot is installed to the main support 2. Sliding of the carriage(s) allows to contact respective tulip heads 130 (see also FIG. 8) of anchors 13 anchored into the bone, respectively.

The rotational support 36 defines a joint axis and is designed to receive a pin 55 of the first pivotable support portion 5. The carriage 32 is provided with holes 33, 34 for receiving respective guide rails 20, 21 to allow the sliding adjustment along directions A.

FIG. 3 shows the first pivotable support portion 5, which in this embodiment comprises an elongated rod 50, and which is attached to the first fixation 3 device by means of joint 52 attached to one end of rod 50. The joint 52 has two protruding parts 53, 54 provided with holes through which the pin 55 extends, which is adapted to be received by guide 36 of the first fixation device 3. The pin 55 may have one or two threads in order to be held in place when installed to the guide 36. The pin 55 and the guide 36 define a vertical axis 91 of rotation around which the elongated rod 50 may pivot. The axis 91 of rotation or the axis 92 of rotation, or both axes, according to this embodiment are parallel to pivot axis 9, but other inclined configurations may be envisaged as well. The elongated rod 50 has a flat portion 51 that allows a sliding adjustment of the third fixation device 6, wherein the flat portion 51 inhibits a rotation of the fixation device 6 around an axis of the rod 50. Further, the fixation device 6 basically comprises a carriage 62 and a screw 61 which fixes the position of the third fixation device 6 along the rod 50.

The third fixation device 6 further has a receiving part 63 including a cylindrical opening 64 configured to receive a portion of a Schanz screw 17, which situation is shown in FIG. 13, for example. The Schanz screw is inserted into the tibia. The fixation of the Schanz screw within the cylindrical hole 64 of the receiving part 63 is secured by a screw 65. This connection provides for the third and final fixation point between the bone assembly and the targeting device.

Sliding adjustment of the third fixation device 6 along the rod 50 is possible in directions B shown in FIGS. 3 and 13.

FIG. 4A shows details of the second pivotable support portion 7, which allows the operator, for example a surgeon or others, to determine the center point or pivot axis 9 for the circular arc-shaped path of the tube portion 12 with drill bit 126 at the tip of the tubular body 125. The second pivotable support portion 7 includes an elongate shaft member 70, a C-shaped receiving portion 71 at its one end, and a rotational support 72 protruding vertically at its other end section 7 a. The C-shaped receiving portion is adapted to engage with a cylindrical portion of the second fixation device 4 arranged above the pinch wheel 41 and a bottom of the carriage 42, which part is not shown in detail in FIG. 2.

To allow a fine adjustment for the position of the pivot axis 9, miniature ribs 73 are provided on an upper surface of the C-shaped receiving portion 71 as shown in FIG. 4B, which offer a tactile response to the surgeon and also a more secure rotational adjustment of the second pivotable support portion 7. A locking mechanism provided at the second fixation device 4 allows fixation of the rotational shaft member position once it has been finally determined by the operating personnel, surgeon or any other staff, etc. Such determination is carried out using a drill jig 10 as shown in FIG. 14 and described with reference to FIG. 6 below.

FIG. 5 shows the pivoting device 8 and the drill arrangement with drill tool 11 and tube portion 12 with drill bit in more detail. The pivoting device 8 comprises a joint part 83 with protruding parts 86 protruding horizontally and holes 86 provided therein such as to be pushed upon the pin-like rotational support 72 of the second pivotable support portion 7. As a consequence, the pivoting device 8 is restricted to a substantially horizontal pivoting movement around the pivot axis 9 with respect to the main support 2. Details of the movement and drilling process are depicted in FIGS. 15 and 16.

The pivoting device 8 is embodied with, for example, two parallel rods 81, 82 extending from the joint part 83. At the other end of the rods 81, 82, a ring 84 is integrally formed which is configured to hold and receive the tube portion 12 of the drill arrangement. A screw 85 may secure the tube portion 12 to the pivoting device 8 when the tubular body 125 is received in the ring 84.

The tube portion 12 comprises the circular arc-shape tubular body 125 having a predetermined radius of curvature r_(c), which corresponds to its distance from the pivot axis 9, i.e., the total length of the pivoting device 8 from the pivot axis and joint 83 through rods 81, 82 up to the central axes of the ring 84 and of the tubular body 125, respectively. Pivoting of the pivoting device 8 moves the tube portion 12 along its own arc-shaped longitudinal central axis. The radius of curvature r_(c) is in one specific embodiment equal to or larger than 130 mm and equal to or smaller than 240 mm, and—in further embodiments—more preferably equal to or larger than 140 mm, or equal to or larger than 150 mm, and/or more preferably equal to or smaller than 210 mm.

At the tip of the tube portion 12, the drill bit 126 that allows drilling into the bone material is provided. The drill bit 126 is driven via a, e.g., spiral drive cable that is configured to be rotated inside the tubular body 125. At the other end of the drive cable, an adaptor of the drill tool 11 is provided that transfers rotational motion from a motor (not shown) of the drill tool 11 to the drive cable. Details of a drill arrangement comprising a drill tool and similar to that as used herein is described in detail in reference US 2010/0292722 A1, which is fully incorporated herein by reference.

A handle 114 of the drill device 11 allows the surgeon to grip the drill device and to forward the same along with the pivot arm 8 such as to advance the drill bit 126 and the tube portion 12 into the bone. Operation keys 111, 112 and 113 allow the surgeon to adjust the drill strength, moot and direction, respectively. Numeral 110 indicates a battery, the drill device 11 shown as a cordless drill tool.

FIG. 6 shows the drill jig 10 which has a tubular section 102 that is vertically passed over the rotational support 72 of the shaft 7. As noted above, drill jig 10 may be replaced by the pivoting device 8 during use, or may provided in addition to the same. Accordingly, the drill jig 10 has the same pivot axis 9 as the pivot device 8 which holds the drill arrangement. Moreover, the drill jig 10 has a horizontal arm 100, which has a length corresponding to that of the pivoting device 8, and a jig portion provided at the end of the arm 100. The jig portion 101 indicates a positioning of the bore to be drilled within the bone assembly located below during use of the targeting device, see FIG. 14. As a consequence, the circular arc-shaped jig portion 101 substantially pivots along the same circular path as the tube portion 12 with drill bit 126 and tubular body 125. This construction allows the surgeon top recognize the position of the bore to be drilled with respect to the bone assembly (herein: calcaneus, talus and tibia), and in response thereto, to reposition the shaft 7 and pivot axis 9, if corrections are needed.

It may be noted that the jig portion 101 is visible in X-ray, and the targeting device may be used in conjunction an X-ray tool to allow the surgeon overlying the jig portion 101 with bones visible in X-ray.

The method of using the targeting device and drilling device is shown in FIGS. 8 through 16. A first step is shown in FIG. 8, wherein the heel to be immobilized is prepared and anchors 13 provided with tulip heads 130 as described above are respectively fixed medially at the talus 15 and the calcaneus 14, respectively. It may be noted that the bone anchor corresponding to the calcaneus is inserted into an axial end face thereof, and not into a plantar end face thereof.

While FIG. 8 shows a side view, FIGS. 9 and 10 show a front and backside view, respectively.

As shown in FIG. 11, Kirschner wires 17 indicated as dashed lines are applied to reposition the bones or fragments of bones, respectively.

In a next step, shown in FIG. 12A, the heel is mounted to the main support 2 of the targeting device 1 between the two fixation devices 3, 4 such that ball heads 38, 47 face the respective tulip heads 130 of the bone anchors. It may be noted that the configuration allows the right foot to be installed to the device in the same manner as the left foot, i.e., in both cases the foot is mounted in a horizontal posture.

Further, vertical parts 39 and 45 of the first and second fixation devices provide a height to the pins 37, 46 and ball heads 38, 47, respectively, such that the pivoting plane of pivoting device 8, which is also the plane of the tube portion 12 and the arc-shaped bore to be drilled, intersects the bone assembly in a medial orientation, that allows the bore to securely extend through the calcaneus, talus and tibia. The height of pins 37, 46 or ball heads 38, 47 may differ from each other.

In this embodiment, the vertical height of pin 37 and ball head 38 of the first fixation device with respect to a plane, in which the three fixation devices move and/or a plane, in which the first and second pivotable support portion 5 and 7 rotate, or a plane in which the pivoting device 8 rotates (each of these planes being parallel to each other in this embodiment), is larger than the vertical height of pin 46 and ball head 47 by a specific distance in vertical direction. This advantageously guarantees an inclination of the orientation of the foot and bone assembly with respect to the plane of the arc-shaped bore to be drilled as noted above, when the bone anchors 13 are inserted a most suitable position in respective bones 14, 15 as shown in FIGS. 8-10.

Next, the tulip head 130 of the bone anchor 13 inserted into calcaneus 14 is snapped on the ball head 47 of the second fixation device 4, first, see FIG. 12B. Then, carriage 32 of the first fixation device 3 is moved towards the talus such that the tulip head 130 of the bone anchor 13 which has been inserted into the talus 15 is snapped on the ball head 38 of the first fixation device 3. Then, the position of carriage 32 along guide rails 20, 21 is locked. At this stage, a 2-point fixation is achieved.

Next, as shown in FIG. 13, a Schanz screw 17 is transversally fixed into the tibia and the first pivoting device 5 is attached to the first fixation device 3 provided at main support 2 being rotatable around axis 91. The third fixation device 6 is then slid to receive a head portion of the Schanz screw 17. The receiving part 63 of the third fixation device 6 is locked and the position of carriage 62 along elongated rod 50 is locked as well. At this step, a 3-point fixation has been established.

As shown in FIG. 14, the second pivotable support portion 7 is attached to the main support 2 (see arrow C in FIG. 14), and the drill jig 10 with its tubular portion 102 is mounted to rotational support 72 of the second pivotable support portion 7. Then, the rotational position of the second pivotable support portion 7 is determined (see arrow D) by bringing the jig portion 101 of drill jig 10 in coincidence with a desired position for the bore within the assembly, by overlay of jig portion 101 over the heel (see arrow E). For this purpose, an X-ray tool allows the operator, or surgeon or others, to recognize the position of respective bones, whereby the jig portion 102 and its scale overlaid is easily visible. The optional rib pattern 73 allows fined adjustment. Once the ideal rotational position has been determined, the second pivotable support portion 7 is locked.

As shown in FIG. 15, the drill jig 10 is removed and replaced (see arrow F) with the drill arrangement including drill tool 11 and tube portion 12 with circular arc-shaped tubular body 125 and drill bit 126. Drill tool 11 is then operated to rotate drill bit 126 and pivoting device 8 is advanced clockwise (see arrow G). Drill bit 126 enters the calcaneus 14 through its end face.

As shown in FIG. 16, an end point is determined by a scale provided at the tube in comparison with a determination that has been made based on a scale provided on the jig portion 101. Thereby, a circular arc-shaped bore has been cut into the calcaneus through the talus into the tibia.

As shown in FIG. 17, the hindfoot is then removed from the frame and main portion, the anchors 13 and the Schanz screw 17 may also be removed and a nail 19 can be inserted into the circular arc-shaped bore thus formed.

The targeting device or its components may be formed from any suitable material, in particular stainless steel, titanium, titanium alloys, or biocompatible plastic or elastomer materials, etc. Rubber or similar materials providing grip may also be used.

The targeting device may also be provided as a kit in conjunction with the bone anchors as described herein.

In the embodiment shown above, the tube portion 12 is designed to have a circular arc shape. However, according to a modification, the arc-shape may also depart from being circular.

For example, the radius of curvature r_(c) may vary along the central axis of the tube portion 12 or may attain different values for specific segments of the same. According to another modification, the pivoting movement may be established by a combined translational (e.g., radial) and rotational movement of the tube portion in order to achieve an arc-shaped bore hole.

In the embodiment above, the main support 2 is provided by two guide rails 20, 21. According to modifications, just one guide rail, or a larger platform may be provided, wherein the fixation devices may be adjusted by other means, e.g., by a ratchet, or a set multiple fixing holes within the platform.

In the embodiment above, the first and second pivotable support portions 7 and 8 are provided to be connected to the main support 2 via joints. However, according to modifications, the frame including main support 2, and the first and second pivotable support portions 7 and 8 may also be provided as one single element, which allows translational or rotational positioning of the at least three fixation devices on a common platform as described above.

In the embodiment above, the three fixation devices are provided as parts separate from the main support. However, according to modifications, one or more of the fixation devices may also be provided as integral parts of the main support or frame, wherein the main support or frame as a whole allows to adjust the mutual distance between the fixation devices, or their mutual rotational position.

In the embodiment above, specific arrangements for receiving portions and bone anchors have been described. However, according to modifications, it is also possible that other connection and fixation mechanisms are employed. For example, each of the at least three fixation devices may comprise a ball head connectable to a tulip head of a bone anchor. Likewise, the bone anchor may comprise the ball head and one or more of the fixation devices includes the tulip head. Further, one or more of the bone anchors may be connected to a rod or plate, and the rod or plate is received by the receiving portion of the respective fixation device.

Moreover, according to another modification, 4, 5, 6 or even more fixation devices may be provided to the targeting device.

In the embodiment above, a targeting device for drilling a bore in the human hindfoot is described din detail. However, the targeting device as proposed herein is also applicable to other parts of the human body. Moreover, the bore drilled using the targeting device does not necessarily require to be provided with a nail. Rather, other applications such as forming an access to a specific part in front, within or behind any bone of the human body are also encompassed by the teaching as described herein. 

1. A targeting device for guiding a drill arrangement for forming an arc-shaped bore in an assembly of adjacent bones or bone fragments, comprising: a support frame; a pivoting device mounted to the support frame and being arranged to receive the drill arrangement and to allow a pivoting movement of the drill arrangement along an arc-shaped path having a predetermined radius of curvature r_(c) around a pivot axis; wherein the support frame is provided with at least three fixation devices each configured to fix one of the bones or fragments of the bone assembly, respectively, to define a fixed position in space of the bone assembly with respect to the pivoting device when the bone assembly is installed to the support frame.
 2. The targeting device of claim 1, wherein a first one and a second one of the at least three fixation devices provided on a main support, which includes at least one guide configured to allow a slidable adjustment of a position of one fixation device with respect to the other fixation device.
 3. The targeting device of claim 2, wherein a third one of the fixation devices is provided being slidably arranged on a first pivotable support portion prior to locking, said first pivotable support portion arranged to be rotatable with respect to the main support within a single plane.
 4. The targeting device of claim 3, wherein one or more of the at least three fixation devices includes a receiving portion arranged to be receive a portion of a bone anchor configured to be anchored in a respective bone or fragment of the bone assembly.
 5. The targeting device of claim 4, wherein the first and second fixation devices are provided with a receiving portion shaped as a spherical ball and arranged to cooperate as a snap-on mechanism with a hollow tulip head of the bone anchor, respectively.
 6. The targeting device of claim 4, wherein the third fixation device includes a receiving portion formed as a hole for receiving a rod-shaped head of a Schanz screw to be anchored into the bone.
 7. The targeting device of claim 2, wherein the pivoting device, which is arranged to allow a pivoting movement of the drill arrangement, is provided being rotationally supported on a second pivotable support portion, wherein the second pivotable support portion is itself pivotable with respect to the main support within a single plane in order to adjust a position of the rotational support for the pivoting device relative to the bone assembly, wherein an angular position of the second pivotable support portion with respect to the main support can be locked.
 8. The targeting device of claim 7, wherein the first pivotable support portion is configured to be connected to the first fixation device; and/or the second pivotable support portion is configured to be connected to the second fixation device.
 9. The targeting device of claim 7, further comprising: a drill jig for indicating a position of the circular arc-shaped bore, wherein the drill jig is configured to be rotationally supported on the second pivotable support portion such as to pivot around the same pivot axis as the pivoting device.
 10. The targeting device of claim 9, wherein said drill jig comprises a portion having an arc-shape which has the radius of curvature r_(c) for allowing to determine the position of the bore to be drilled with respect to the bone assembly, when the bone assembly is installed to the support frame.
 11. The targeting device of claim 1, comprising: the drill arrangement mountable to the pivoting device, wherein the drill arrangement further comprises: a drill device arranged to provide a rotational movement; a circular arc-shaped tubular body having an end connected to said drill device, and through which a means for transferring the rotational movement extends; a drill bit provided at another end of the tubular body opposite to the end connected to the drill device, the drill bit being connected to the means for transferring the rotational movement such as to facilitate drilling into the bone assembly responsive to rotation transferred from the drill arrangement upon advancing the drill arrangement into the bone, when the pivoting device is pivoted around the pivot axis.
 12. The targeting device of claim 11, wherein: the arc-shaped tubular body extends with the predetermined radius of curvature r_(c) substantially along its entire length, wherein the arc-shape is circular.
 13. The targeting device of claim 11, wherein: when the drill arrangement is mounted to the targeting device, said circular arc-shaped tubular body is configured to extend within the plane that is defined by directions of movement of the at least three fixation devices.
 14. The targeting device of claim 1, wherein the radius of curvature r_(c) is at least 130 mm.
 15. The targeting device of claim 1, wherein the radius of curvature r_(c) is equal to or less than 240 mm. 